If you're going to use the w3schools XSLT tutorials, watch out. They have recently changed them so that XSLT version 1 and version 2 are combined in one tutorial, and they don't distinguish which is which. And since you are likely still using version 1, accidentally putting a version 2 feature into your code is going to be confusing.
My cellmate was this tiny ad:
a bit of art, as a gift, that will fit in a stocking